I'll give you the standard polygrapher reply.

Gee, you must of just had a bad examiner.

Gee, you must be one of the those rare false positives cases.  But hey, no test is perfect.   

Gee, you must be making this up.  After all, the test is 98% accurate!

Gee, I don't know.  There are so many variables that could have  gone awry, but the test is still 98% accurate.

What makes you feel so ENTITLED to a job in LE?  What makes you so SPECIAL?

I don't know about the butt puckering detection part of your question, but there are other CM you can use.  Count backwards from 113 in increments of 6.  Bite the side of your tongue.

TC

Two years ago I was subjected to a Polygraph test for a job as a Police Officer.  I disclosed everything and told the whole truth and nothing but the truth....  You guessed it... FALSE POSITIVE..  When asked if I had ever taken drugs I answered with no (truth),  the examiner told me that with out a doubt I was lying!! Also when asked questions on handeling stolen goods the examiner told me I was lying..  I have been invited back to re-apply and I am super worried about this stupid interogation.  The LE agency uses the  Lafayette LX 4000 to screen applicants.  Do any of you guys know if this device can detect the butt squeeze counter measure.   
I'll be damned if i'm gonna let this magic box stand the the way of my lifetime dream of becoming a Police Officer!